Refining petroleum oil



Patented Nov. 10, 1942 REFINING PETROLEUM OIL Wayne A. Proell, Chicago, Ill., and Richard S.

McClaughry, Hammond,

Ind., assignors to StandardOil company. Chicago, 111., a corporation of Indiana No Drawing. Application March 6, 1940,

Serial No. 322,588 1 11 Claims.

This invention relates to the refining of oils. More particularly it relates to a novel process for increasing the resistance of oils, particularly lubricating oils, to oxidation of sludgirig.

Deterioration of petroleum oils dueto oxidation during storage or use is a well known phenomenon as are likewise various methods for decreasing the susceptibility of oil to such deterioration. In face, laboratory tests have been devised to determine the stability of petroleumoils when subjected to conditions ordinarily leading to such deterioration. One of the best of these is known as the Indiana oxidation test (National Petroleum News, September 13,1933, page 30).

Known methods of increasing the oxidation stabilities of lubricating oils are not entirely satisfactory, however, in that they fall far short of. increasing oxidation resistance to the optimumamount and in that such treatments usually have a deleterious effect on other properties of the oil such as viscosity increase and acidity develop-- ment when used.

It is, therefore, an object of this invention to provide a new and improved method for increasing the resistance to oxidation of viscous petroleum oils. A further object is to provide a method for improving the oxidation stabilities of viscous petroleum oils, particularly lubricating oils, without adversely affecting any other characteristic of the oil. Another object is to provide such a process in which not only the oxidation stability but also other properties such as viscosity index are improved. Other objects, advantages and uses of our invention will appear hereinafter.

It has been found that these objects may be accomplished by oxidizing a viscous petroleum oil which is deficient in oxidation stability and thereafter treating the oxidized material with alkali and chemically reducing it, after which it may be clayed or otherwise treated, if desired, to improve its color or other characteristics. A preferred embodiment of this invention consists in treating petroleum lubricating oil in the manner set forth.

In order that the invention may be better understood, the following specific examples are given which are to be construed as illustrative only and not as limiting the scope of the invention:

Example I Six hundred grams of a solvent refined distillate lubricating oil, described more particularly below, were oxidized for 69 hours at 341 F. by 55 blowing a slow stream of air through the oil. The oil was then heated for two hours with 300 cubic centimeters of alcoholic 5% potassium hydroxide. A moderate amount (about 5 grams) I of tarry material separated from the oil during this treatment. Following this treatment the oil was separated from the causticsolution, transferred to a flask and boiled under reflux for one hour with a solution consisting of 200 cubic centimetersof 5% hydrochloric acid in 50% alcohol, 5 grams ferrous sulfate, 0.05 gram copper sulfate and 10 grams of metallic zinc. Thereafter the reaction mass was transferred to a separatory funnel by means of which the acid was removed and the oil was then washed several times with dilute alkali and water. The clean oil was then washedwith alcohol, dried, and heated to 300 F. To the heated oil 5 grams of Super Filtrol clay was added and the oil was filtered. The claying treatment was repeated twice. The treated oil was quite clear and about the same color as the initial material.

The distillate lubricating oil treated in this example was an S. A. E. 30 oil which had been dewaxed with propane and Chlorex extracted to increase its viscosity index. Prior to the treatment described in this example it had an Indiana oxidation test of 124 hours while after treatment this Indiana oxidation test had been increased to 210 hours which is extremely high. Furthermore, after 240 hours treatmentunder Indiana oxidation test conditions the product'treated as described in this example appeared free flowing and non-tarry, though the sludge content was fairly high (i. e. 50 milligrams per 10 grams of oil). Very few commercial lubricating oils have an Indiana oxidation test of 200 or more hours and most of those which have this characteristic become very viscous and :tarry near the ZUU hour mark even though the sludge COllLGl'it may be low.

Emample 11 Six hundred grams of a solvent refined distillate lubricating oil similar to that treated in Example I but having an initial Indiana oxidation test of 120. hours, were oxidized for 67 hours at 341 F. by blowing a slow stream of air through the oil. The, oil was then heated with 300 cubic centimeters of alcoholic 5% potassium hydroxide until-the alcohol boiled for about two hours. Following this, the oil and alcohol were cooled and separated and the oil was added to a solution consisting of 200 cubic centimeters of 5% hydrochloric acid in 50% alcohol, 5 grams ferrous sulfate and 0.5 gram copper sulfate in a flask and the mixture was heated to between '100 and 200 F. Ten grams of metallic Zinc were then added and the mixture was warmed under reflux for one hour. Thereafter, the reaction mass was transferred to a separatory funnel from which the acid was removed and the oil was washed several times with dilute alkali solution and alcohol. After drying, it was heated to 300 F. and clayed until the desired color was obtained.

The resulting product had an Indiana oxidation test of 200 hours. It was also found that the viscosity index had been materially improved by the treatment from 89.5 to 92. Furthermore, it was found that the stability of the oil to viscosity increase had been greatly improved. Usually in the Indiana oxidation test the viscosity increases to very high values by the time sludging occurs but in the case of the product made in accordance with this example the Saybolt Universal viscosity only increased from 577 seconds to 1905 seconds ten hours after the oil had sludged.

As the term is used in this specification and in the appended claims the point at which an oil sludges is the point at which it yields 0.1% of sludge. More particularly an oil sludges when it reaches a content of milligrams of sludge per 10 grams of oil as measured by the Indiana oxidation test. The time required to cause sludging under given conditions is the time required to form 10 milligrams of sludge per 10 grams of oil under the temperature and other oxidation conditions prevailing.

Although the time and temperature of oxidation set forth in the above examples are preferred, the invention is not limited to these particular conditions, thus the oxidation time may vary from about 10% to about 150% of the time required to cause sludging in the oil at the tem-' perature employed. The actual time chosen will depend in part, at least, upon the oxidation characteristics of the oil and upon the extent of the improvement which it is desired to effect, and the temperature may be any convenient temperature which gives a suitably rapid oxidation of the oil without undue decomposition, for instance this connection it is pointed out that tests in which the oxidation times at the same temperature were less than in the above examples have indicated that the extent of improvement is closely related to the extent of oxidation, increasing as it increases, at least, under some conditions. If desired, the oxidation treatment may be assisted by theuse of catalystsalthough, as indicated above, satisfactory results may be obtained in their absence. Suitable catalysts include metal soaps, clay, ferric chloride and other catalysts known to promote oxidation.

The alkali treatment can be effected in a variety of ways although again that set forth in the examples is preferred. Thus, it can be effected at normal or elevated temperatures in alcoholic or aqueous solution or in solution in a mixture of water and alcohol. Itcan also be carried out by heating the oil with or distilling it in the presence of solid alkali. The oxidation and alkali treatment steps can be carried out simultaneously, 1. e., the oil can be oxidized in the presence of alkali.

Preferably the alkali used is an alkali metal hydroxide such as sodium or potassium hydroxide. The alkali may, however, be supplied in other forms if desired, for instance ammonium hydroxide and the alkali metal carbonates can be used. As indicated in the examples, after the alkali treatment the oil is cooled if necessary and separated from the treating solution.

Reduction, which preferably follows the alkali treatment, likewise is not limited to the particular process specifically'disclosed although the latter does represent a preferred procedure. Reduction is a well known chemical procedure and alternative methods need not be detailed here at great length. They include, for example, the use of other acids with the same or other metals or, in general, the use of other hydrogen-producing combinations as well as the use of reducing agents which act by means of a change in valence without the release of hydrogen. A catalyst for the reduction may or may not be employed as desired and the treatment may be carried out at normal or elevated temperature. The preferred method is not strictly limited to that described in the above examples but may be more broadly stated to include the use of a dilute aqueous or alcoholic solution of hydrochloric acid (about 5 percent) containing small amounts of iron and cop-.

per salts at a temperature of about 100 to about 200 F. in the presence of a moderate amount of tion of the undesirable residual oxidized constituents of the oil but also eliminates, in whole or in part, another step of the process, viz., that of adding acid after the alkali treating step to neutralize the alkali and provide excess acid for hydrogen production.

Following the oxidation and alkali treatment and reduction steps the oil is worked up by conventional methods to render it suitable for use. Thus, it is separated after the reduction step from the reducing agent and washed to eliminate 1500 to F" p eferably t 40p? F, In that part of the reducing composition not taken away by simple separation, particularly if the re- "ducing composition is acidic in nature. As in the preferred embodiment the treated oil is washed with alkali and water in order to neutralize it. It can be and usually must be then subjected to conventional refining treatments, such as claying, for example, to improve its color and to complete the neutralization of the oil.

The invention is particularly applicable to the manufacture of lubricating oils, transformer oils,

and the like which are subjected to relatively high temperatures in use with the resulting high a tendency towards oxidation of the oil. Our invention is applied in the above illustrations to a solvent refined oil-and is particularly adapted to the treatment of such oilsbut it may also be applied to raw and non-extracted distillates which may then be further refined as desired or to other types of oils which lack adequate sta bility towards oxidation.

- The advantages of this process will be apparent from the above. A method is provided by which the oxidation stability of viscous petroleum oils deficient therein may be improved not only as afiects sludge formation but also as afiects increase in viscosity and without adversely affecting other desirable properties of the oil. In fact, as disclosed in Example II, other properties of the oil, such as viscosity index, are markedly improved. Deterioration of certain oils due to oxidation is a serious drawback to their use and thus the present invention provides a means for increasing the'usefulness of oils.

Other-processes aimed at the same difllculty have been disclosed previously but none has been shown to possess the advantages of the present process, i. e., phenomenal increase in oxidation resistance accompanied by improvement in other properties and by no adverse affect upon them.

The use of the three steps of oxidation, alkali treatment and reduction in combinationappears to be essential to the production of oil having maximum improvement in oxidation character istics. A fourth step oi claying' is normally necessary in order to produce an oil of satisfactory color. Thus oxidation for 67 hours at 341 F. followed only by clay treating reduced the Indiana oxidation test of the oil treated in Example II from 120 to 73 hours. Alkali treatment alone as in Example II without oxidation or reduction did not change the test of the oil beyond experimenal error. Treatment as in Example II except that the reduction step was omitted only increased the Indiana oxidation test from 120 hours to 132 hours. when treated according to the process described herein, viscous petroleum oils are suited to the same uses for which they would have been used without the treatment but they will perform more satisfactorily because of their increased stability to oxidation and because of their improved viscosity index. These improved properties, however, do extend the field of usefulness of the oils. Thus they can be employed under more severe conditions where oils not so treated would fail or would have such a short useful life as to render their employment impracticable from an economic standpoint.

It will be apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof and, therefore, it is not intended to be limited except as indicated in the appended claims.

We claim:

1. A process for increasing the stability to oxidation of viscous solvent refined distillate petroleum oil which comprises oxidizing said oil for about 70 hours at about 341 F. by blowing a slow stream of air through the oil, then heating the oil with a dilute solution in alcohol of an alkali of the group consisting of sodium and potassium hydroxides at the boiling point of the mixture for about two hours, then cooling and separating the oil and treating solution, adding the separated oil to a dilute solution of hydrochloric acid in a solvent of the group consisting of water and alcohol which solution contains ferrous and copper salts, heating the mixture, adding a moderate amount of metallic zinc and warming for about one hour, and thereafter removing the oil, neutralizing, washing and claying it until a desired color is achieved.

2. A process as described in claim 1 further characterized in that the oil treated is a lubricat- 3. A process for increasing the stability to oxidation of a viscous petroleum oil deficient therein which comprises oxidizing the oil by treatment with a gas containing free oxygen, neutralizing the oxidized oil by treatment with an alkali metal hydroxide and then chemically reducing the oxidized and neutralized oil by treatment with at least one reducing agent.

4. A process as described in claim 3 furthe characterized in that the oil is a lubricating oil.

5. A process as described in claim 3 further characterized in that the oil treated is a solvent refined distillate oil. I 6. A process as described in claim 3 and further comprising clay treating the oil to produce a light colored oil.

. 7. A process of manufacturing a transformer oil of high oxidation stability which comprises oxidizing a transofrmer oil stock of low oxidation stability by treatment with a gas containing free oxygen, neutralizing the oxidized oil by treatment with an alkali metal hydroxide, chemically reducing the oxidized and neutralized oil by treatment with at least one reducing agent and then clay treating the chemically reduced oil.

8. A process for increasing the stability to oxidation of a viscous hydrocarbon distillate petroleum oil deficient therein which comprises oxidizing the oil by treatment with a gas containing free oxygen at elevated temperatures for a prolonged period of time, neutralizing the oxidized oil by treatment with an alkali metal hydroxide and then chemically reducing the oxidized and neutralized oil by treatment with at least one re ducing agent.

9. A process for increasing the stability to oxidation of a viscous distillate petroleum oil deficient therein which comprises oxidizing the oil chemically reducing the oxidized and neutralized oil by treatment with at least one reducing agent, and thereafter separating the agent from the treated oil, neutralizing and washing the oil and finally clay treating the oil to obtain a desired color.

10. A process as described in claim 9 wherein the neutralizing step consists in'heating the oxidized oil to elevated temperatures with a solution of an alcoholic alkali metal hydroxide.

ii. A process as described in claim 9 wherein the chemical reduction step consists in heating the oil with a dilute aqueous solution of a strong acid in the presence of a hydrogen-displacing metal.

WAYNE A. PROELL. RICHARD S. MCCLAUGHRY. 

